Abstract

Liquid crystals may be classified in two major categories, namely, thermotropic and lyotropic. Thermotropic liquid crystals are commonly prepared by heating organic compounds, whereas lyotropic liquid crystals are made by mixing two or more components. Thermotropic liquid crystals are mainly of interest in this paper. They have been classified as nematic (threadlike) and smectic (soapy). Most commercial applications have focused on thermotropic liquid crystals; however, lyotropic liquid crystals are important in the detergent industry and in living systems. Thermotropic and lyotropic liquid crystals show polymorphism. The properties and structure of the different polymorphic forms are discussed. The two most-active areas of applications of liquid crystals are nondestructive testing and display media; both are considered. Liquid crystals have been used as solvents in structure determination (nmr) in chromatography and in study of chemical kinetics.

© 1973 Optical Society of America

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References

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  1. H. Zocher, Mol. Cryst. Liq. Cryst. 7, 172 (1969).
  2. G. W. Gray, Molecular Structure and the Properties of Liquid Crystals (Academic, New York, 1962).
  3. A. Saupe, Angew. Chem. (Int. Ed. Engl.) 7, 97 (1968).
    [CrossRef]
  4. G. H. Brown, Chem. Rev. 57, 1049 (1957).
    [CrossRef]
  5. G. H. Brown, Anal. Chem. 41, 26A (1969).
    [CrossRef]
  6. G. H. Brown, Am. Sci. 60, 64 (1972).
  7. W. Kast, in Landolt-Börnstein, Vol. 2, Part 2a, 6th ed.(Springer, Berlin, 1960), pp. 226–335.
  8. G. H. Brown, J. W. Doane, and V. D. Neff, Crit. Rev. Solid State Sci. 1, 303 (1970).
    [CrossRef]
  9. A. de Vries, Mol. Cryst. Liq. Cryst. 16, 311 (1972).
    [CrossRef]
  10. G. H. Heilmeier, L. A. Zanoni, and L. C. Barton,Proc. IEE 56, 1162 (1968).
    [CrossRef]
  11. M. Schadt, and W. Helfrich, Appl. Phys. Lett. 18, 127 (1971).
    [CrossRef]

1972 (2)

G. H. Brown, Am. Sci. 60, 64 (1972).

A. de Vries, Mol. Cryst. Liq. Cryst. 16, 311 (1972).
[CrossRef]

1971 (1)

M. Schadt, and W. Helfrich, Appl. Phys. Lett. 18, 127 (1971).
[CrossRef]

1970 (1)

G. H. Brown, J. W. Doane, and V. D. Neff, Crit. Rev. Solid State Sci. 1, 303 (1970).
[CrossRef]

1969 (2)

H. Zocher, Mol. Cryst. Liq. Cryst. 7, 172 (1969).

G. H. Brown, Anal. Chem. 41, 26A (1969).
[CrossRef]

1968 (2)

G. H. Heilmeier, L. A. Zanoni, and L. C. Barton,Proc. IEE 56, 1162 (1968).
[CrossRef]

A. Saupe, Angew. Chem. (Int. Ed. Engl.) 7, 97 (1968).
[CrossRef]

1957 (1)

G. H. Brown, Chem. Rev. 57, 1049 (1957).
[CrossRef]

Barton, L. C.

G. H. Heilmeier, L. A. Zanoni, and L. C. Barton,Proc. IEE 56, 1162 (1968).
[CrossRef]

Brown, G. H.

G. H. Brown, Am. Sci. 60, 64 (1972).

G. H. Brown, J. W. Doane, and V. D. Neff, Crit. Rev. Solid State Sci. 1, 303 (1970).
[CrossRef]

G. H. Brown, Anal. Chem. 41, 26A (1969).
[CrossRef]

G. H. Brown, Chem. Rev. 57, 1049 (1957).
[CrossRef]

de Vries, A.

A. de Vries, Mol. Cryst. Liq. Cryst. 16, 311 (1972).
[CrossRef]

Doane, J. W.

G. H. Brown, J. W. Doane, and V. D. Neff, Crit. Rev. Solid State Sci. 1, 303 (1970).
[CrossRef]

Gray, G. W.

G. W. Gray, Molecular Structure and the Properties of Liquid Crystals (Academic, New York, 1962).

Heilmeier, G. H.

G. H. Heilmeier, L. A. Zanoni, and L. C. Barton,Proc. IEE 56, 1162 (1968).
[CrossRef]

Helfrich, W.

M. Schadt, and W. Helfrich, Appl. Phys. Lett. 18, 127 (1971).
[CrossRef]

Kast, W.

W. Kast, in Landolt-Börnstein, Vol. 2, Part 2a, 6th ed.(Springer, Berlin, 1960), pp. 226–335.

Neff, V. D.

G. H. Brown, J. W. Doane, and V. D. Neff, Crit. Rev. Solid State Sci. 1, 303 (1970).
[CrossRef]

Saupe, A.

A. Saupe, Angew. Chem. (Int. Ed. Engl.) 7, 97 (1968).
[CrossRef]

Schadt, M.

M. Schadt, and W. Helfrich, Appl. Phys. Lett. 18, 127 (1971).
[CrossRef]

Zanoni, L. A.

G. H. Heilmeier, L. A. Zanoni, and L. C. Barton,Proc. IEE 56, 1162 (1968).
[CrossRef]

Zocher, H.

H. Zocher, Mol. Cryst. Liq. Cryst. 7, 172 (1969).

Other (11)

H. Zocher, Mol. Cryst. Liq. Cryst. 7, 172 (1969).

G. W. Gray, Molecular Structure and the Properties of Liquid Crystals (Academic, New York, 1962).

A. Saupe, Angew. Chem. (Int. Ed. Engl.) 7, 97 (1968).
[CrossRef]

G. H. Brown, Chem. Rev. 57, 1049 (1957).
[CrossRef]

G. H. Brown, Anal. Chem. 41, 26A (1969).
[CrossRef]

G. H. Brown, Am. Sci. 60, 64 (1972).

W. Kast, in Landolt-Börnstein, Vol. 2, Part 2a, 6th ed.(Springer, Berlin, 1960), pp. 226–335.

G. H. Brown, J. W. Doane, and V. D. Neff, Crit. Rev. Solid State Sci. 1, 303 (1970).
[CrossRef]

A. de Vries, Mol. Cryst. Liq. Cryst. 16, 311 (1972).
[CrossRef]

G. H. Heilmeier, L. A. Zanoni, and L. C. Barton,Proc. IEE 56, 1162 (1968).
[CrossRef]

M. Schadt, and W. Helfrich, Appl. Phys. Lett. 18, 127 (1971).
[CrossRef]

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Figures (7)

Fig. 1
Fig. 1

(a) Schematic diagram of the molecular arrangement in a uniformly oriented nematic liquid crystal. (b) Schematic diagram of the molecular arrangement in a uniformly oriented twisted nematic liquid crystal (cholesteric). This structure possesses an infinite-fold screw axis. (c) Schematic diagram of molecular packing in a smectic A liquid crystal. This structure has an infinite-fold symmetry axis. (d) Schematic diagram of the molecular arrangement in a smectic C liquid crystal.

Fig. 2
Fig. 2

Nematic schlieren texture.

Fig. 3
Fig. 3

Smectic fan-shaped texture.

Fig. 4
Fig. 4

Mosaic texture found in a tilted smectic B.

Fig. 5
Fig. 5

Plots of typical curves of flux density (relative) as a function of Bragg angle. Smectic A is plot (a) and smectic B is plot (b).

Fig. 6
Fig. 6

Schematic representation of lamellar packing.

Fig. 7
Fig. 7

Schematic representation of the packing pattern of rod-like particles.

Tables (4)

Tables Icon

Table I Abbreviated listing of classes of thermotropic liquid crystals.

Tables Icon

Table II Polymorphism of lyotropic liquid crystals (abbreviated listing).

Tables Icon

Table III Information on a few compounds that form liquid crystals.

Tables Icon

Table IV Polymorphism of thermotropic liquid crystals.

Equations (3)

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S = 1 2 ( 3 cos 2 θ 1 ) ,
crystal H 2 O + H 2 O lamellar liquid-crystal structure H 2 O + H 2 O hexagonal liquid-crystal structure H 2 O + H 2 O micellar phase H 2 O + H 2 O true solution .
Crystal cool heat smectic B cool heat smectic C cool heat smectic A cool heat nematic liquid crystal cool heat isotropic liquid .